Many modern applications such as data warehousing, global information systems, and electronic commerce require accessing a data source that stores data arranged in a source schema, and then using that data at a target that requires the data to be arranged in a target data schema. For example, product data that is stored in one schema for optimal storage efficiency may have to be accessed and reformatted into another schema for Web commerce.
Data exchange is the problem of materializing an instance that adheres to a target schema, given an instance of a source schema and a schema mapping that specifies the relationship between the source and the target. A schema mapping is a specification that describes how data structured under one schema (a source schema) is to be transformed into data structured under a different schema (the target schema). Schema mappings are ubiquitous in information integration systems.
The application of schema mapping arises often when data is transferred between independent applications that do not have the same data format. Conventional approaches exist for mapping data from a source schema to a target schema. Because of the extensive use of schema mappings, it has become important to develop a framework for managing schema mappings and other metadata.
Although conventional schema mapping frameworks have proven to be useful, it would be desirable to present additional improvements. Conventional frameworks lack an inverse operator; i.e., an inverse schema mapping. Developing an inverse schema mapping is not straightforward. A schema mapping is not simply a function that maps an instance of a source schema to an instance of a target schema. Rather, for each source instance, the schema mapping may associate many target instances. Furthermore, for each target instance, there may be many corresponding source instances.
Having mapped data from a source schema to a target schema, in many applications an inverse mapping is useful. For example, data may be migrated from one application (a source application) to another application (a target application) using schema mapping. The user may decide to slop using the target application if, for example, the developer stops supporting the target application, the user determines the target application is not providing desired functionality, etc. In this example, an inverse mapping is useful for rolling back data to the source application. An inverse schema mapping can accomplish this data “roll back”. A user may further decide in the process of mapping a source schema to a target schema to “roll back” one step of the schema transformation. No method currently exists for generating an inverse schema mapping.
What is therefore needed is a system, a computer program product, and an associated method for performing an inverse schema mapping. The need for such a solution has heretofore remained unsatisfied.